Category: 4. Protection And Switchgear

t is essential to protect high capacity transformers against external and internal electrical faults. External Faults in Power Transformer External Short Circuit of Power Transformer The short – circuit may occur in two or three phases of electrical power system. The level of fault current is always high enough. It depends upon the voltage which…

History of SF6 SF6 or sulfur hexafluoride gas molecules are combined by one sulfur and six fluorine atoms. This gas was first realized in the year 1900 in the laboratories of the Faculte de Pharmacie de, in Paris. In the year of 1937, General Electrical Company first realized that SF6 gas could be used as…

Definition of Switchgear A switchgear is a generic term which includes all the switching devices associated with power system protection. It also includes all devices associated with control, metering and regulating of electrical power systems. Assembly of such devices in a logical manner forms switchgear. In other words systems used for switching, controlling and protecting…

Generally electrical switchgear rated upto 1KV is termed as low voltage switchgear. The term LV Switchgear includes low voltage circuit breakers, switches, off load electrical isolators, HRC fuses, earth leakage circuit breaker, miniature circuit breakers (MCB) and molded case circuit breakers (MCCB) etc i.e. all the accessories required to protect the LV system. The most…

As the length of electrical power transmission line is generally long enough and it runs through open atmosphere, the probability of occurring fault in electrical power transmission line is much higher than that of electrical power transformers and alternators. That is why a transmission line requires much more protective schemes than a transformer and an…

There are always a chance of suffering an electrical power system from abnormal over voltages. These abnormal over voltages may be caused due to various reason such as, sudden interruption of heavy load, lightening impulses, switching impulses etc. These over voltage stresses may damage insulation of various equipments and insulators of the power system. Although,…

Motor protection circuit breakers are a specialized type of electrical protection device that is designed specifically for electric motors, like their name implies. Electric motors have plenty of applications and are used to drive mechanical devices of all types, so it is very important to protect them adequately with MPCBs. The following are just a…

Loss of field or excitation can be caused in the generator due to excitation failure. In larger sized generator, energy for excitation is often taken from a separate auxiliary source or from a separately driven DC generator. The failure of auxiliary supply or failure of driving motor can also cause the loss of excitation in…

This is to be noted that, the star point or neutral point of stator winding of an alternator is grounded through an impedance to limit the ground fault current. Reduced ground fault current causes less damage to the stator core and winding during ground or earth fault. If the ground impedance is made quite high,…